Electron-discharge device



. July 17, 1928. 1,677,355

W. A. M DONALD ELECTRON DISCHARGE DEVICE Origihal Filed April 9, 192

INVENTOR ATTORNEYS of a vacuum tube of Patented daily i7, 192.

UNHTEID STATEg innate parent @FFHQ.

m A. MACDONALD, OF LITTLE NE, NEW Y0, ASSIGNOR T HAZELTINE GUBPOMTION, 0F JERSEY CITY, NEW amsnx, A GORPOMTION 0F DEAWARE.

Original application filed April 9, 1926, Serial No. 100,826. Divided. and this application filed June 21,

1927. Serial No. 200,391.

This invention relates to electron discharge devices, or vacuum tubes, and circuit arrangements in which the same may be employed.

in amplifiers and radio receivers, especially those in which radio-frequency currents are amplified, it is known that the inherent capacity between the grid and plate electrodes of the amplifying tubes causes undesirable couplings between the various circuits which tend to produce undesirable Oscillations. Various circuit arrangements have been devised to neutralize the eflect of this inherent coupling capacity, and in all these arrangements the circuits are designed to neutralize a predetermined inherent capacity. It has been found in practice, however, that there is lack of uniformity of this inherent capacity even among vacuum tubes of the same type, so that it is difficult to efi'ect the desired neutralization.

In accordance with the present invention, it is proposed to add a separate adjustable condenser which will supplement and increase the effective value of the inherent interelectrode capacity which is to be neutralized. The electrostatic capacity of this condenser is adjustable so that all the tubes of a type may be made exactly alike even though there may be variations in the natural capacity between certain of the electrodes. Furthermore, with a given neutralizing capacity, may efi'ectively be varied by adjustment of this supplemental condenser. The present specification is a division of my specification Serial No. 100,826, filed April 9, 1926.

In the drawings:

Fig. 1 represents a vertical cross-section of a vacuum tube in which the present invention is incorporated.

F ig. 2 shows a perspective view of the base Fig. 1 in which the terminal contacts extend through the bottom.

Fig. 3 shows a side elevation of a portion of a vacuum tube in which the terminal contacts project through the side of the base, and in which two adjustable supplementalcondensers are provided.

Fig. 4 shows a section taken on the line 4-4 of Fig. 3 showing in detail the adjustable contacts by which the capacities of two supplemental condensers may be varied.

the degree of neutralization 24 Fig. 5 is a circuit arrangement of one form of radio receiver in WhlCll vacuum tubes provided with the present invention may be em loyed.

eferring especially to Fig. 1, there is shown an evacuated envelope 1 in the press of which is mounted a plate 13 and a. grid 14 consisting of a fine wire wound spirally upon two wire supports. Within the grid and plate there is located a filament 26 suitably supported by wires mounted in the press. A base, generally designated 2, including a collar 3 is cemented to the envelop 1 by means of insulating material 4 through which the lead-in wires of the various electrodes extend. The plate 13 is electrically connected by a lead-in wire 18 to a threaded sleeve 8 secured in an opening at 7 in the collar 3 of the base. Wire 17, soldered to this sleeve, is connected to the plate terminal contact 5 extending through the insulating material 24. This material supports the various terminal contacts of the tube and closes the end of the collar 3 to which it is secured.

The lead-in wire 15, connected to the grid, is soldered to a lug 9 staked inan opening in the collar 3. This lug terminates in a condenser plate or armature 10 for a purpose to be described, and is also electrically connected by the wire 16 to the plate contact 6 extending through the insulating material A threaded'member 11 terminating in a condenser plate or armature 12 is threaded in the sleeve 8 and has its free end provided with a kert to receive a screw driver passed through the opening at 7 by which it is adjustable to vary the spacing, and hence the electrostatic capacity, between the armatures 10 and 12. It will be noted that the capacity between these armatures supplements the inherent capacity existing between the grid 1% and the plate 13. If desired, the opening at 7 may be filled with, sealing wax, or other suitable substance 7, after the capacity is adjusted, so that the adjustment cannot be easily tampered with.

In Fig. 3 there is shown a modified form of the invention wherein the contacts of the tube 19, and 21 extend through the side of the base for use with a vacuum tube socket such as is disclosed in my co-pending application Serial No. 31,736, filed May 21, 1925. As shown in Fig. 4, the armature 10 is connected to the grid contact 20 while the adjustable armature 12 is threaded in the plate contact 19. In certain circuit arrangements, it-is desirable to have tubes in which the inherent capacity between the filament and grid or plate, is uniform. For this reason, an armature 27 adjustable with respect to armature 10 and electrically connected to filament contact 21, is provided, whereby an adjustable supplemental capacity is provided between the plate and filament. It will thus be understood that by means of the present invention the inherent capacity between grid and plate, the inherent capacity between filament and grid, and the inherent capacity between plate and filament can be individually adjusted to any desired standards.

Referring to Fig. 5 there is diagrammatically indicated the circuit arrangement of a radio receiver having one stage of radiofrequency amplification and a detector D. The dot-and-dash line between the primary and secondary coils of the coupling transformer 30, together with the suggested break in the connection between neutralizing condenser 29 and the mentioned secondary coil, is intended to indicate that additional highfrequency amplifying stages similar to that shown may precede the detector. As was previously stated, there is represented an inherent capacity 25 existing between the plate electrode 13 and the grid 14, of tube 28. -In order to neutralize the effect of this inherent capacity the circuits are arranged toinclude a neutralizing capacity 29 in accordance with the arrangement disclosed in the Patent No. 1,533,858 to Louis A. Hazeltine. The vacuum tube 28, between whose grid electrode 14 and plate electrode 13 there exists inherent capacity 25, is provided with means introducing a supplemental capacity according to the pl'esent'invention, including the armature 10 and the adjustable armature 12 effectively connected in parallel with the inherent ca pacity between the mentioned electrodes of the tube.

It will be readily recognized that by the present invention the inherent capacities of various tubes may be rendered exactly uniform, whereby the tubes may be interchangeable for use in neutralized radio-frequency amplifying stages, or in other circuits which require precise values of inter-electrode capacities. For manufacturing or other reasons. it is sometimes desirable to utilize a. reasonably large neutralizing capacity. In such event the use of a supplemental gridplate capacity, according to this invention, makes possible the employment of a neutral izing capacity of any desired size while allowing also for any desired turns ratiobetween the plate-circuit coil and the neutralizing coil, as required by the neutralization equation given in the mentioned Hazeltine patent. The degree of neutralization may then effectively be adjusted by variation of either the neutralizing capacity or the supplemental capacity, or by adjustment of both.

I claim:

1. An amplifying system embodying a plurality ofvacuum tubes, each of said tubes having a grid and a-plate between which inherent capacity exists, an input circuit connected to the grid, and an output circuit connected to the plate of each tube, a condenser. supplementing said inherent capacity con-- nected in parallel thereto, and a second condenser, one terminal of which is connected to the grid of one of said tubes, the other terminal of said second condenser being connected to the input circuit of another of said tubes.

2. An amplifying system embodying a plurality of vacuum tubes coupled in cascade, each tube being provided with a grid and a plate, an arrangement for neutralizing the inherent capacity coupling existing between the grid and the plate of each,tube including a supplemental condenser connected between the grid and the plate of the tube in each stage, and a capacity effectively connected between the grids of the vacuum tubes of successive stages.

3. An amplifying system embodying a plurality of vacuum tubes, each of said tubes being provided with electrodes including a grid and a plate coupled by an inherent electrostatic capacity, an input circuit connected to each grid, an output circuit connected to each plate, one input circuit being electrically linked to an output circuit, a condenser connected between the grid and the plate of one of said tubes, a second condenser eonnected to the grid electrode of said last mentioned tube and to the input circuit of another of said tubes, and means for adjusting said second condenser so that the current flowing therethrough will be equal to and opposite in phase to the current flowing through the electrostatic capacity through said first mentioned condenser.

4. An amplifying system embodying a plurality of vacuum tubes, the output circuit of one tube being coupled to the input circuit of the next succeeding tube by means including an output-circuit coil. each'tube being provided with grid and plate electrodes between which inherent coupling capacity exists, a -supplemental condenser connected in parallel to the inherent grid-plate capacity of one of said tubes, and an electrical network for neutralizing the coupling effect of the total electrostatic capacity existing between the grid and plate electrodes of said and last-mentioned tube, comprising a capacity effectively connected between the grid of said last-mentioned tube and a coil electromagnetically coupled to said output-circuit coil,

enses and means for ad usting the capacity of said an plemental condenser whereby in effect to ad ust the degree of neutralization.

5. An amplifying system embodying a plurality of vacuum tubes, being provided with electrodes including a grid and a plate coupled by an inherent electrostatic capacity, an input circuit connected to each grid and an output circuit connected to each plate, the output circuit of the first of said tubes being electrically linked with the input circuit of the second of said tubes, a supplemental condenser connected between the grid and plate electrodes of the first of said tubes, a capacity effectively connected between the grid of said first tube and the input circuit of said second tube, and means including said supplemental condenser for adjusting the total electrostatic capacity between the grid and plate electrodes of said first tube whereby the current flowing through said total electrostatic capacity will be substantially equal to and opposite in phase to the current flowing through the capacity effectively connected between the grid of said first tube and the input circuit of said second tube.

6. A radio receiver including an amplifying vacuum tube having a grid electrode,

a plate electrode and a filament system, an.

input circuit including a coil connected between the grid electrode and the filament system, and an output circuit including a coil connected between the plate electrode and the filament system, said coil connected in the output circuit being coupled to an input-circuit coil connected between the grid electrode and filament system of a succeeding vacuum tube, inherent capacity between said grid and plate electrodes, a supplemental capacity connected between said grid and plate electrodes to augment said inherent capacity, an electrical network for neutralizing the coupling effect of the total capacity existing between said grid and plate electrodes comprising a capacity effect vely connected in series with a coil between one of said electrodes and the filament system, said last-named coil being electromagnetically coupled to another of said coils connected between the other of said electrodes and the filament system, said coupled coils being so related to each other that the high-potential terminal of one coil is of opposite polarity to the' high-potential terminal of the other coil, and means for adjusting at least one of said capacities whereby in efi'ect to adjust the degree of neutralization.

7. A radio receiver including an amplify ing vacuum tube having a grid electrode, a

plate electrode and a filament system, an

each of said tubes,

and the filament system,

input circuit including a coil connected between the grid electrode and the filament system, and an output circuit including a coil connected between the plate electrode and the filament system, said coil connected in the output circuit being coupled to an input-circuit coil connected between the grid electrode and filament system of a succeeding vacuum tube, inherent capacity between said grid and plate electrodes, a supplemental condenser connected between said grid and plate electrodes to augment said inherent capacity, an electrical network for neutralizing the coupling effect of the total capacity existing between said grid and plate electrodes comprising a capacity efli'ec tively connected in series with a coil between one of said electrodes and the filament'system, said last-named coil being electromagnetically coupled to another of said coils connected between the other of said electrodes and the filament system, said coupled coils being so related to each other that the high-potential terminal of one coil is of opposite polarity to the high-potential terminal of the other coil, and means for adjusting the capacity of said supplemental condenser whereby in efiect to adjust the degree of neutralization.

8. A radio receiver including an amplifyingvacuum tube havin a grid electrode, a plate electrode and a filament system, an input circuit including a coil connected between the grid electrode and the filament system, and an output circuit including a coil connected between. the plate electrode said coil connected in the output circuit being coupled to an input-circuit coil connected between the grid electrode and the filament system of a succeeding vacuum tube, the high-potential terminal of the input-circuit coil connected to said succeeding vacuum tube being of opposite polarity to the high-potential terminal of the coil in said outputcircuit, inherent capacity between said grid and plate electrodes, a supplemental condenser connected between said grid and plate electrodes to augment said inherent capacity, means for neutralizing the coupling effectof the coupling capacity existing betweensaid grid and late electrodes, comprising a capacity effectively connected between said first-mentioned grid electrode and the inputcircuit coil of said'succeeding vacuum tube, and means for adjusting the capacity of said su plemental condenser whereby in efiect'to ad ust the degree of neutralization.

In testimony whereof I aflix my signature.

WILLIAM A. MAoDONALD. 

